SU957758A3 - Process for producing silicon dioxide - Google Patents

Abstract

1513890 Finely divided oxides of metals and/or silicon DEUTSCHE GOLDUND SILBERSCHEIDEANSTALT 22 Oct 1975 [30 July 1975] 43314/75 Heading C1A A process for the production of finely divided oxides of metals (Ti and Al are specified) and/or silicon by the hydrolytic reaction of a volatile chloride thereof in a flame comprises feeding the chlorides in a mixture with hydrogen and with air or oxygen to a flame burning from a burner in a reaction chamber, reacting them in the flame, keeping the burner mouth free by passing hydrogen thereover, passing the oxide aerosol thus formed together with through a subsequent cooling system and separating the oxide from the process gases in a separation apparatus, chlorine formed in the flame reaction being reduced with hydrogen during cooling of the reaction gases to a temperature below the reaction temperature of the hydrogen with the oxygen in the reaction gas.

Description

This invention relates to a process for the preparation of highly dispersed silicon dioxide used in various fields of technology. A known method for producing silicon dioxide by high-temperature hydrolysis-of silicon chloride in an environment of oxygen and combustible gases, cooling the gaseous hydrolysis products and the subsequent separation of highly dispersed silicon dioxide with a particle size of 10-20 mm. By carrying out the hydrolysis in a nitrogen atmosphere, the formation of free chlorine is eliminated. The disadvantage of this method is the increased consumption of reagents due to hydrolysis under nitrogen. Known method 2 is the production of silicon dioxide by high-temperature hydrolysis of chloride silicon in a medium consisting of hydrogen- and oxygen-containing gases, cooling gas-gas products, treating them with water vapor and then with nitrogen and followed by the separation of silica. A highly dispersed product is obtained with a specific surface of 200 and a content of free chlorine of O, 1 wt.%. The disadvantages of this method are the use of nitrogen and the increased content of free chlorine in the product. The purpose of the invention is to reduce the chlorine content in the product and simplify the process by eliminating the introduction of nitrogen into the process. The goal is achieved by the fact that in the known method of producing silicon dioxide, which consists in high-temperature hydrolysis of silicon chloride in hydrogen-oxygen-containing gases, cooling the gaseous reaction products with subsequent separation of silicon dioxide, before the separation of silicon dioxide, the gaseous hydrolysis products are cooled to 500-650 0 and treat them with hydrogen. The temperature mode of cooling, which differs from the prototype, and the operation of treating gaseous products with hydrogen reduce the chlorine content in the product to 0.07% and obtain a highly dispersed product with a specific surface of 200 Mvr. Furthermore, the method allows utilization of hydrogen chloride to produce concentrated salts of the acid.

At a temperature below, the rate of reduction of chlorine with hydrogen is low, and the chlorine content in the product is elevated - 6.7%. At a temperature above, the hydrogen consumption is increased due to its interaction with 5 oxygen, and the chlorine content in the product does not decrease. The interaction in the gaseous products of the reaction of chlorine with hydrogen should be carried out under the action of ultraviolet light.

Example. 2,000 kg of C1, 648 of hydrogen and 1.900 nm / h of air are fed to the aerosol burner. 22 hydrogen is fed to the burner housing. 706 kg / h of highly dispersed persistent silicic acid with a specific surface of 200 are obtained. The amount of free chlorine in the reaction gas is 7.5%. The reaction gas is cooled before and 70 hydrogen are introduced into it. .jn The amount of freeJlOij is reduced to 0.07%. Then, pp}} /: the finely dispersed SiOj is separated by the reaction. foot gas. .% "

Example # 1. The process is carried out in a similar manner to Example} 1. b BCG / m of hydrogen is introduced into the reaction gases cooled to 460 ° C. The amount of free chlorine in this case decreases from 7.5 to 6.7%.

Example 3. The process is carried out analogously to Example 1, except for the HHeM that after carrying out the chemical transformation 70 hydrogen is introduced into the reaction gases cooled to bWo. The amount of free chlorine remains unchanged.

The proposed method allows to simplify the process by eliminating the consumption of additional reagents (water vapor, nitrogen).

Claims (2)

Invention Formula The method of obtaining silicon dioxide by high-temperature hydrolysis in the environment of hydrogen- and oxygen-containing gases, cooling the gaseous hydrolysis products followed by separation of the product, characterized by the fact that, in order to reduce the chlorine content in the product and simplify the process, before gaseous products are cooled to 500-650 ° C, and then they are treated with hydrogen. Sources of information taken into account in the examination .one. Patent of Germany 1210421, cl. 12 G 5/01, publ. 1966 p. 2. Unaccepted application for Germany No. 2153671, cl. 12 N 1/02, published, 1973.